Our study is designed to examine predictors of obesity in 56 normal weight prepubertal females. These children have been admitted twice to the GCRC for 3 days each and to the 24-hour whole-room indirect calorimeter twice. Their ad libitum caloric intake has been recorded and they have undergone duplicate baseline testing of the following measurements: energy expenditure, body composition, biochemical profiles, and physical activity. As well, each of their parents have undergone the following: weight history and activity questionnaires, anthropometric measurements, abdominal computer tomography, and dual energy x-ray absorptiometry. We plan to repeat the measurements in the children yearly. By doing so we will be able to track EE and body composition through their pubescence, to relate them to parental characteristics, and to document temporal changes which will help establish cause versus effect relationships.